1. Field of the invention
The present invention relates to a method of, and an apparatus for, carrying out a loopback test in an exchange. In particular, the present invention relates to a method of, and an apparatus for, carrying out a loopback test to diagnose devices that form a channel system of an exchange with the use of a loopback function provided for each of the devices.
2. Description of the Related Art
FIG. 9 shows devices that form a channel system of an exchange. The devices are a tester (TSTU) 9-1, subscriber terminals 9-21 to 9-23, individual devices (IND-A to IND-C) 9-31 to 9-33, common devices (COM#0 to COM#2) 9-41 to 9-43, and a switching unit (SW) 9-5.
Sub-highways (SHWO, SHW1) 9-61 and 9-62 are connected to the lower side of the common device 9-41, and sub-highways (SHWO, SHW1) 9-63 and 9-64 are connected to the lower side of the common device 9-42. Network highways (NHWO to NHW2) 9-71 to 9-73 connect the common devices 9-41 to 9-43 to the switching unit 9-5. The devices also include unmounted subscriber devices IND-x and IND-y.
A mark ".OR right." represents a loopback part through the drawings. Numerals attached to this mark like .OR right.0, .OR right.1, and .OR right.2 correspond to sub-highway or network highway numbers connected to the lower side of a given device. For example, ".OR right.0" is a loopback part for a sub-highway 0 (SHW0) or a network highway 0 (NHW0).
A mark ".OR right.C" is a loopback part for a highway connected to the higher side of a given device. A mark ".OR right.L" is a loopback part of an individual device for a subscriber channel end.
The tester 9-1 sends a test signal such as a voice signal or an ATM cell signal to devices to be tested, receives the test signal looped back by the devices, analyzes the received signal, and diagnoses the devices.
The terminals 9-21 to 9-23 terminate channels for subscribers A to C, respectively, and have each a loopback part for looping back a test signal.
The individual devices 9-31 to 9-33 are subscriber devices for interfacing the subscribers A to C with channels and have each a loopback part .OR right.L for the subscriber and a loopback part .OR right.C for the common device.
The common devices 9-41 to 9-43 are line concentrators for multiplexing signals from the individual devices and demultiplexing signals to the individual devices. The common devices have each loopback parts .OR right.0 and .OR right.1 for the individual devices, as well as a loopback part .OR right.C for the switching unit 9-5.
The switching unit 9-5 has a function of switching a main signal (communication information) transmitted through the network highways according to a destination and has loopback parts .OR right.0 to .OR right.2 for the network highways 9-71 to 9-73.
Japanese Unexamined Patent Publication Nos. 2-97151, 3-104366, 4-157842, 4-207544, and 7-250076, for example, disclose a technique of testing and diagnosing devices arranged in an exchange by installing loopback parts in each device, sending a test signal from a tester, looping back the test signal at the loopback parts, analyzing the looped-back signal at the tester, and determining whether or not the devices are sound.
FIGS. 10 and 11 explain loopback tests carried out on devices that form a channel system of an exchange, according to a prior art. In FIGS. 10 and 11, the same parts as those of FIG. 9 are represented with like reference numerals. FIG. 10 tests a path from a tester 9-1 to a connection end of a common device 9-42 for a sub-highway 9-63. FIG. 11 tests a path from the tester 9-1 to a connection end of the common device 9-42 for a sub-highway 9-64.
In FIG. 10, a path P1 indicated with a thick line is set from the tester 9-1 to a loopback part .OR right.0 of the common device 9-42 for the sub-highway 9-63 through a common device 9-41, network highway 9-71, switching unit 9-5, and network highway 9-72, and then, from the loopback part .OR right.0 of the common device 9-42 to the tester 9-1 through the same route.
A loopback part cl of the switching unit 9-5 for the network highway 9-72 is activated, and the tester 9-1 transmits a test signal, which is looped back by the loopback part .OR right.1 of the switching unit 9-5. The tester 9-1 receives the looped-back signal, analyzes it, and determines whether or not the path to the loopback part .OR right.1 of the switching unit 9-5 is sound.
The loopback part .OR right.1 of the switching unit 9-5 is released, and a loopback part .OR right.C of the common device 9-42 is activated. The tester 9-1 sends a test signal, which is looped back by the loopback part .OR right.C of the common device 9-42. The tester 9-1 receives the looped-back signal, analyzes it, and determines whether or not the path to the loopback part .OR right.C of the common device 9-42 is sound.
The loopback part .OR right.C of the common device 9-42 is released, and the loopback part .OR right.0 of the common device 9-42 for the sub-highway 9-63 is activated. The tester 9-1 transmits a test signal, which is looped back by the loopback part .OR right.0 of the common device 9-42. The tester 9-1 receives the looped-back signal, analyzes it, and determines whether or not the path to the loopback part .OR right.0 of the common device 9-42 is sound.
Thereafter, the path P1 is released, and a path P2 indicated with a thick line in FIG. 11 is set from the tester 9-1 to the loopback part .OR right.1 of the common device 9-42 for the sub-highway 9-64 and from the same loopback part .OR right.1 to the tester 9-1. The loopback part .OR right.1 of the common device 9-42 is activated, and the tester 9-1 transmits a test signal to this loopback part .OR right.1. The tester 9-1 receives a looped-back signal from the same loopback part .OR right.1, analyzes it, and determines whether or not the path to the loopback part .OR right.1 is sound.
FIG. 12 shows the steps of testing the common devices mentioned above. Steps 12-1 to 12-8 test the path P1 of FIG. 10. More precisely, step 12-1 sets an outgoing path from the tester 9-1 to the individual device 9-32 for the subscriber B through the common device 9-41, switching unit 9-5, and common device 9-42.
Step 12-2 sets a return path from the individual device 9-32 to the tester 9-1 through the same route as the outgoing path.
Step 12-3 activates the loopback part .OR right.0 of the common device 9-42 so that a signal may be transferred from the outgoing path to the return path.
Step 12-4 instructs the tester 9-1 to send a test signal, receive a looped-back signal, and analyze the signal. Step 12-5 instructs the tester 9-1 to stop the test signal. Step 12-6 receives an analysis result from the tester 9-1 and examines it.
Step 12-7 releases the loopback part .OR right.0 of the common device 9-42. Step 12-8 releases the outgoing and return paths, to complete the test of the path P1 of FIG. 10.
Steps 12-9 to 12-12 test the path P2 of FIG. 11. More precisely, step 12-9 sets an outgoing path from the tester 9-1 to the individual device 9-33 for the subscriber C through the common device 9-41, switching unit 9-5, and common device 9-42.
Step 12-10 sets a return path from the individual device 9-33 to the tester 9-1 through the same route as the outgoing path.
Step 12-11 activates the loopback part .OR right.1 of the common device 9-42 so that a signal may be transferred from the outgoing path to the return path.
Step 12-12 executes the same processes as those executed in steps 12-4 to 12-8 to send a test signal, receive the test signal looped back by the loopback part .OR right.1 of the common device 9-42, analyze the received signal, examine the analysis result, release the loopback part .OR right.1 of the common device 9-42, release the outgoing and return paths, and complete the test.
Setting paths and loopback parts will be explained in detail. FIG. 13 explains setting a path in the switching unit 9-5 with the use of a time switch. Devices used to set a path are a write data selector (multiplexer) 13-1, a voice memory 13-2, a read data latch (demultiplexer) 13-3, an address counter 13-4, and a control memory 13-5.
Voice data of the subscriber A is sent to the subscriber B, and voice data of the subscriber B is sent to the subscriber A, to establish a conversation between the subscribers A and B. Namely, paths are set between the subscribers A and B. To achieve this, a voice memory address B-adr of the subscriber B is set at an address #A for the subscriber A in the control memory 13-5. A voice memory address A-adr of the subscriber A is set at an address #B for the subscriber B in the control memory 13-5.
Voice data A-data and B-data from the subscribers A and B are temporally divided and multiplexed by the multiplexer 13-1 and are written into the voice memory 13-2 in synchronization with the address counter 13-4. The voice data A-data from the subscriber A is written at the address #A in the voice memory 13-2, and the voice data B-data from the subscriber B is written at the address #B in the voice memory 13-2 in the sequence of, for example, A-data and B-data.
The control memory 13-5 stores a sequence of reading data out of the voice memory 13-2. Namely, addresses stored in the control memory 13-5 are read in synchronization with the address counter 13-4, and the addresses are used to read the voice data out of the voice memory 13-2.
More precisely, the voice data B-data and A-data are read out of the voice memory 13-2 in the sequence of B-data and A-data, and the read data are stored in the demultiplexer 13-3, which provides the subscriber A with the voice data B-data from the subscriber B, and the subscriber B with the voice data A-data from the subscriber A.
Writing the address B-adr of the subscriber B of the voice memory 13-2 at the address #A for the subscriber A in the control memory 13-5 is equal to setting a path from the subscriber B to the subscriber A, and writing the address A-adr of the subscriber A of the memory 13-2 at the address #B for the subscriber B in the memory 13-5 is equal to setting a path from the subscriber A to the subscriber B.
FIG. 14 shows any one of the loopback parts in the exchange of FIGS. 9 to 11. The loopback part has a selector 14-1, an upward path 14-2 coming from a subscriber, an upward path 14-3 going toward the exchange, a downward path 14-4 going toward the subscriber, and a loopback instruction line 14-5.
The selector 14-1 usually transmits a signal from the upward path 14-2 to the upward path 14-3. In response to a loopback instruction during a loopback test, the selector 14-1 transmits a signal from the downward path 14-4 to the upward path 14-3. Any loopback part in the individual devices, common devices, and switching unit has the structure of FIG. 14.
Setting paths and loopback parts according to the prior art will be explained in detail with reference to FIGS. 15 to 18. FIG. 15 shows devices that form a channel system of an exchange. The structure of FIG. 15 is a simple model only for explanation purposes. An actual channel system involves many devices, channels, and loopback parts. FIGS. 16 to 18 are flowcharts showing the steps of carrying out loopback tests according to the prior art.
In FIG. 15, there are a channel housing unit 15-1 for a subscriber A, a loopback part (LP-A) 15-11 incorporated in the unit 15-1, a channel housing unit 15-2 for a subscriber B, a loopback part 15-21 incorporated in the unit 15-2, a tester 15-3, and a switching unit 15-4. The switching unit 15-4 incorporates loopback parts (LP-a, LP-b, LP-c) 15-41, 15-42, and 15-43 for the subscribers A and B and tester 15-3, respectively, a data multiplexer (MLT) 15-44, a data demultiplexer (DMLT) 15-45, a voice memory 15-46, a control memory 15-47, and a counter (CNT) 15-48.
The voice memory 15-46 has addresses A-adr, B-adr, and C-adr where data from the subscribers A and B and tester 15-3 are written to, respectively. The control memory 15-47 has addresses #A, #B, and #C corresponding to the subscribers A and B and tester 15-3, respectively.
A loopback test according to the prior art must individually set paths and loopback parts for devices to be tested. To test the switching unit 15-4 and channel housing units 15-1 and 15-2, the prior art must execute the steps of FIGS. 16 to 19.
Steps 16-1 to 16-18 test the switching unit 15-4, steps 16-19 to 16-27 test the unit 15-1 for the subscriber A, and steps 16-28 to 16-36 test the unit 15-2 for the subscriber B.
When testing the switching unit 15-4, steps 16-1 and 16-2 set a path TSTU-A from the tester 15-3 to the subscriber A and a path A-TSTU from the subscriber A to the tester 15-3. Steps 16-3 to 16-7 set loopback parts, send a test signal, receive the test signal, analyze the received signal, and release the loopback parts. Steps 16-8 and 16-9 release the paths. Steps 16-10 and 16-11 set a path TSTU-B from the tester 15-3 to the subscriber B and a path B-TSTU from the subscriber B to the tester 15-3. Steps 16-12 to 16-16 set loopback parts, send a test signal, receive the test signal, analyze the received signal, and release the loopback parts. Steps 16-17 and 16-18 release the paths.
When testing the channel housing unit 15-1 for the subscriber A, steps 16-19 and 16-20 again set the paths TSTU-A and A-TSTU. Steps 16-21 to 16-25 set loopback parts, send a test signal, receive the test signal, analyze the received signal, and release the loopback parts. Steps 16-26 and 16-27 release the paths.
When testing the channel housing unit 15-2 for the subscriber B, steps 16-28 and 16-29 again set the paths TSTU-B and B-TSTU. Steps 16-30 to 16-34 set loopback parts, send a test signal, receive the test signal, analyze the received signal, and release the loopback parts. Steps 16-35 and 16-36 release the paths.
In this way, the prior art carries out loopback tests to locate a fault in devices of an exchange by individually setting paths to the devices, sending test signals to the devices, and diagnosing the devices according to the signals. Since recent exchanges have highly integrated devices and large capacity and involve many common devices, the prior art has the problems of:
(1) involving a large number of path setting processes for devices to test, to make the tests intricate and laborious; PA1 (2) limiting a range of devices to test in spite of many paths to be set; and PA1 (3) increasing the number of tests to carry out because recent exchanges incorporate many channels, thereby elongating a testing time.
Maintenance work on an exchange must locate a fault in the exchange and replace a fault unit with a new one. The exchanges incorporate many functional devices among which a fault one must quickly be found and corrected.